For humans in particular, cooperative behavior in a community and, by extension, sexual activity reinforce social bonds between individuals and may form larger social structures.
The resulting cooperation encourages collective tasks that promote the survival of each member of the group.
It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen or vaginal fluids.
Fingering (or digital penetration or digital intercourse) involves the manual manipulation of the clitoris, rest of the vulva, vagina or anus for the purpose of sexual arousal and sexual stimulation; it may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities.
The specificity of questions concerning sexual activity can additionally affect definitions of sexual intercourse or other sexual behaviors.
Another study by the Kinsey Institute sampled 484 people, ranging in ages 18–96.
Other forms of penetrative sexual intercourse include anal sex (penetration of the anus by the penis), oral sex (penetration of the mouth by the penis or oral penetration of the female genitalia), fingering (sexual penetration by the fingers), and penetration by use of a dildo (especially a strap-on dildo).Studies regarding the definition of sexual intercourse sometimes conflict.A 1999 study by the Kinsey Institute examined the definition of sex based on a 1991 random sample of 599 college students from 29 U. states; it reported that while "virtually every college student they surveyed considered penile–vaginal intercourse to be sex," and 19–20% said that anal intercourse was not sex, 60% said oral-genital contact (fellatio, cunnilingus) did not constitute having sex.Learner and Steinberg attribute researchers' focus on penile–vaginal sex to "the larger culture's preoccupation with this form of sexual activity," and have expressed concern that the "widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question [about sexual activity] matches what the researcher had in mind'".It may also be that conceptually conflating sexual activity with vaginal intercourse and sexual function hinders and limits information about sexual behavior that non-heterosexual people may be engaging in, or information about heterosexuals who may be engaging in non–vaginal sexual activity.Virginity loss is often based on penile–vaginal intercourse partly because heterosexual couples may engage in anal or oral sex not only for sexual pleasure, but as ways of maintaining that they are virgins if they have not engaged in the reproductive act of coitus.Similarly, some gay men consider frotting or oral sex as ways of maintaining their virginities, with penile-anal penetration defined as sexual intercourse and resulting in virginity loss, while other gay men may define frotting or oral sex as their main forms of sexual activity.Similarly, a 2003 study published in the Canadian Journal of Human Sexuality focusing on definitions of having sex and noting studies concerning university students from the United States, the United Kingdom, and Australia reported that "while the vast majority of respondents (more than 97%) in these three studies included penile–vaginal intercourse in their definition of sex, fewer (between 70% and 90%) respondents considered penile-anal intercourse to constitute having sex" and that "oral-genital behaviours were defined as sex by between 32% and 58% of respondents".The Centers for Disease Control and Prevention (CDC) stated in 2009 that "although there are only limited national data about how often adolescents engage in oral sex, some data suggest that many adolescents who engage in oral sex do not consider it to be 'sex'; therefore they may use oral sex as an option to experience sex while still, in their minds, remaining abstinent".Religious views on sexuality vary significantly between different religions and sects of the same religion, though there are common themes, such as prohibition of adultery.Reproductive sexual intercourse between non-human animals is more often termed copulation, and sperm may be introduced into the female's reproductive tract in non-vaginal ways among the animals, such as by cloacal copulation.